This logic is dumb. Nadal "owns" Fed 6-2 on outdoor hardcourt, yet no sane Nadal fan claims Nadal is a better outdoor hardcourt player than Federer, because Fed's outdoor hardcourt accomplishments at slam level are so much stronger. What we take from the outdoor H2H (and Nadal's outdoor hardcourt record overall), is that Nadal is an excellent outdoor hardcourter that can beat anyone on his day (even Fed), despite hardcourts being his weakest surface. He could also lose to any player on his day (at least before he matured on the surface), and was for years an inconsistent hardcourt player, despite his ability to win big on the surface. Nadal has beaten Djokovic, an all-time great hardcourt player in a hardcourt slam final, so the fact that he could also beat Fed on outdoor hardcourts shouldn't come as a surprise.
The totality of the H2H, and the huge sampling of matches Fed and Nadal played (30 in all, 20 to Nadal, 8-2 at slams)) tells us that Nadal is the overall better TENNIS player, even though Nadal and Fed both have their prefeerred surfaces. The totality of the Nadal/Davy H2H (5-6) only says that he was not a major rival and gave Nadal a tough time outside major events, nothing more, nothing less. Ignoring context is pretty desperate.
If Davy Had a 6-1 hardcourt record over Nadal at slams, no one would hesitate to say Davy is better. The greatest players peak for slams. It's why Davy is not considered a great player. The 8-2 record at slams between Nadal and Fed is ugly, and he got wins on every surface,